The present invention relates to a semiconductor device, and can be preferably used in a semiconductor device including, for example, a power MOS transistor.
Semiconductor devices including a power MOS (Metal Oxide Semiconductor) transistor, etc., are used to operate electrical components, such as lights, power steering, and power windows mounted in automobiles.
For example, an n-channel power MOS transistor is formed, as an switching element, in an element formation region defined in a semiconductor substrate of the semiconductor device. In the element formation region, a p-type base region, in which a channel is formed, is formed. A p−-type guard ring region is formed in a terminal region surrounding the element formation region. A source electrode is formed on the surface side of the semiconductor substrate, and a drain electrode is formed on the rear side thereof.
An n-type drift region to serve as a drain region is formed in the semiconductor substrate. A p-type column region is formed to protrude from the bottom of the p-type base region toward the n-type drift region. The p-type column regions and the n-type drift regions are formed, for example, to be placed alternately in one direction. This structure is called a superjunction structure. Examples of patent documents in which such a semiconductor device is disclosed include Patent Documents 1 and 2.